A classical reactive potential for molecular clusters of sulphuric acid and water

We present a two-state empirical valence bond (EVB) potential describing interactions between sulphuric acid and water molecules and designed to model proton transfer between them within a classical dynamical framework. The potential has been developed in order to study the properties of molecular clusters of these species, which are thought to be relevant to atmospheric aerosol nucleation. The particle swarm optimisation method has been used to fit the parameters of the EVB model to density functional theory (DFT) calculations. Features of the parametrised model and DFT data are compared and found to be in satisfactory agreement. In particular, it is found that a single sulphuric acid molecule will donate a proton when clustered with four water molecules at 300 K and that this threshold is temperature dependent

Continued fraction digit averages an Maclaurin's inequalities

A classical result of Khinchin says that for almost all real numbers $\alpha$, the geometric mean of the first $n$ digits $a_i(\alpha)$ in the continued fraction expansion of $\alpha$ converges to a number $K = 2.6854520\ldots$ (Khinchin's constant) as $n \to \infty$. On the other hand, for almost all $\alpha$, the arithmetic mean of the first $n$ continued fraction digits $a_i(\alpha)$ approaches infinity as $n \to \infty$. There is a sequence of refinements of the AM-GM inequality, Maclaurin's inequalities, relating the $1/k$-th powers of the $k$-th elementary symmetric means of $n$ numbers for $1 \leq k \leq n$. On the left end (when $k=n$) we have the geometric mean, and on the right end ($k=1$) we have the arithmetic mean. We analyze what happens to the means of continued fraction digits of a typical real number in the limit as one moves $f(n)$ steps away from either extreme. We prove sufficient conditions on $f(n)$ to ensure to ensure divergence when one moves $f(n)$ steps away from the arithmetic mean and convergence when one moves $f(n)$ steps away from the geometric mean. For typical $\alpha$ we conjecture the behavior for $f(n)=cn$, $0<c<1$. We also study the limiting behavior of such means for quadratic irrational $\alpha$, providing rigorous results, as well as numerically supported conjectures.Comment: 32 pages, 7 figures. Substantial additions were made to previous version, including Theorem 1.3, Section 6, and Appendix

Controlled levels of protein modification through a chromatography-mediated bioconjugation.

Synthetically modified proteins are increasingly finding applications as well-defined scaffolds for materials. In practice it remains difficult to construct bioconjugates with precise levels of modification because of the limited number of repeated functional groups on proteins. This article describes a method to control the level of protein modification in cases where there exist multiple potential modification sites. A protein is first tagged with a handle using any of a variety of modification chemistries. This handle is used to isolate proteins with a particular number of modifications via affinity chromatography, and then the handle is elaborated with a desired moiety using an oxidative coupling reaction. This method results in a sample of protein with a well-defined number of modifications, and we find it particularly applicable to systems like protein homomultimers in which there is no way to discern between chemically identical subunits. We demonstrate the use of this method in the construction of a protein-templated light-harvesting mimic, a type of system which has historically been difficult to make in a well-defined manner

Voices from the Desks: Exploring Student Experiences in Counselor Education

The purpose of the qualitative study was to explore the themes that counselor education master’s students perceived as impacting their experience within a counseling program. Counselor education master’s students provided their perceptions of what they attributed to helping or hindering their progress. Themes identified as impacting their experiences were academic environment, finances, job preparation, self-care, life role balance, support, mentoring and advising, and personal growth. Recommendations are provided for counselor educators to consider when structuring programs and interacting with master’s students

Mobile Solar Power Trailer

Construction projects require a substantial amount of power to operate tools and power lights. Traditionally, this power is delivered to the project sites via transmission lines or generators; however, some construction projects must be undertaken in relatively remote areas where the infrastructure is lacking. Additionally, there may be reservations concerning the ethical implications that come with the method by which the power is generated. To provide a solution to bringing sufficient and ethically generated power to remote or urban worksites, this project investigates the design and implementation of a generator that is solar-powered and enclosed in a trailer for transportability. The Mobile Solar Power Trailer (MST) is a trailer mounted with an array of PV panels that doubles as an enclosure for the supporting components required for power generation, energy storage, DC-AC conversion, and the distribution required to support a work site with reliable and adequate power. The scope of this project considers aspects such as efficient use of sunlight, effective positioning of PV panels, adequate energy storage, and appropriate scaling of components to deliver the required power. Cost estimates are included for the final configuration and the overall design

Fibrolamellar hepatocellular carcinoma at a tertiary centre in South Africa

Background: Fibrolamellar carcinoma (FLC) is an uncommon malignant tumour of hepatocyte origin that differs from hepatocellular carcinoma (HCC) in aetiology, demographics, condition of the affected liver, and tumour markers. Controversy exists whether FLC demonstrates a more favourable prognosis than typical HCC. A review of existing literature reveals a dearth of FLC data from the African continent. Methods: We utilised the prospective liver resection database at Groote Schuur Hospital to identify all patients who underwent surgery for FLC between 1990 and 2008. Results: Seven patients (median age 21 years, range 19 - 42, 5 men, 2 women) underwent surgery for FLC. No patient had underlying liver disease or an elevated alpha fetoprotein (AFP) at either initial presentation or recurrence. Six patients had a solitary tumour at diagnosis (mean largest diameter = 12cm), and underwent left hepatectomy (N=2), right hepatectomy (N=1), extended right hepatectomy (N=1), and segmentectomies (N=2). Three patients underwent a portal lymphadenectomy for regional lymphatic tumour involvement. One patient with advanced extrahepatic portal nodal metastasis was unresectable. No peri-operative deaths occurred. Recurrence occurred post resection in all 6 patients. Median overall survival was 60 months, and overall 5-year survival was 4 out of 7 (57%). Post-resection survival (N=6) was 61 months, with a 5-year survival rate of 4 out of 6 (67%). The patient with unresectable disease survived 38 months after tumour embolisation with Lipiodol. Conclusion: Our series suggests that despite (i) a high resection rate of solitary lesions with clear tumour resection margins, and (ii) absence of underlying liver disease, FLC has a high recurrence rate with an ultimately poor clinical outcome. These findings concur with recent international experience of FLC

Acquired resistance to anti-PD1 therapy: checkmate to checkpoint blockade?

Editorial summary Anti-programmed cell death 1 (PD1) immunotherapies are among the most effective anti-cancer immunotherapies available; however, a large number of patients present with or develop resistance to them. Unfortunately, very little is known regarding the mechanisms of resistance to such therapies. A recent study sought to identify mutations associated with resistance to anti-PD1 therapy. Results from this study demonstrated that mutations which affected the sensitivity of tumor cells to T-cell-derived interferons, and mutations limiting tumor-cell antigen presentation, could cause acquired resistance. These findings have significant implications for understanding the mechanisms by which anti-PD1 therapies exert their efficacy, comprehending why and how some patients acquire resistance over time, and ultimately guiding the development of combination therapies designed to overcome, or potentially prevent, the development of acquired immunotherapeutic resistance

Energetic Cost of Ichthyophonus Infection in Juvenile Pacific Herring (Clupea pallasii)

The energetic costs of fasting and Ichthyophonus infection were measured in juvenile Pacific herring (Clupea pallasii) in a lab setting at three temperatures. Infected herring incurred significant energetic costs, the magnitude of which depended on fish condition at the time of infection (fat versus lean). Herring that were fed continually and were in relatively good condition at the time of infection (fat) never stored lipid despite ad libitum feeding. In feeding herring, the energetic cost of infection was a 30% reduction in total energy content relative to controls 52 days post infection. Following food deprivation (lean condition), infection caused an initial delay in the compensatory response of herring. Thirty-one days after re-feeding, the energetic cost of infection in previously-fasted fish was a 32% reduction in total energy content relative to controls. Body composition of infected herring subsequently recovered to some degree, though infected herring never attained the same energy content as their continuously fed counterparts. Fifty-two days after re-feeding, the energetic cost of infection in previously-fasted fish was a 6% reduction in total energy content relative to controls. The greatest impacts of infection occurred in colder temperatures, suggesting Ichthyophonus-induced reductions in body condition may have greater consequences in the northern extent of herring's range, where juveniles use most of their energy reserves to survive their first winter

Effects of Environmental Temperature on the Dynamics of Ichthyophoniasis in Juvenile Pacific Herring (Clupea pallasii)

The effects of temperature and infection by Ichthyophonus were examined in juvenile Pacific herring (Clupea pallasii) maintained under simulated overwinter fasting conditions. In addition to defining parameters for a herring bioenergetics model (discussed in Vollenweider et al. this issue), these experiments provided new insights into factors influencing the infectivity and virulence of the parasite Ichthyophonus. In groups of fish with established disease, temperature variation had little effect on disease outcome. Ichthyophonus mortality outpaced that resulting from starvation alone. In newly infected fish, temperature variation significantly changed the mortality patterns related to disease. Both elevated and lowered temperatures suppressed disease-related mortality relative to ambient treatments. When parasite exposure dose decreased, an inverse relationship between infection prevalence and temperature was detected. These findings suggest interplay between temperature optima for parasite growth and host immune function and have implications for our understanding of how Ichthyophonus infections are established in wild fish populations